Many modern portable electronic devices include actuators to provide alerts and notifications. As one common example, many mobile phones include a rotary vibration motor with an eccentric weight that spins rapidly in order to produce a vibration. This vibration may alert a user to an incoming telephone call when the phone is muted, for example. The vibration takes the place of the standard audio alert and may be felt by the user if he or she is touching the phone. However, the vibration may still be noisy in certain environments and this may be undesirable.
Further, many rotary mass actuators not only create an audible buzz, but also an undesirable feel. Because rotary mass actuators spin up to an operating state and then wind down to a rest state, they constantly shake the enclosure of the electronic device. This feels “buzzy” to a user and there is little, if any, control over the haptic output of such a device other than to control the amplitude of the output or to provide discrete outputs with an unacceptably long time between the outputs.
Certain linear actuators are used instead of rotary mass actuators in some electronic devices. Linear actuators may deliver a more crisp haptic output and are quieter in certain cases. However, many such linear actuators are relatively large and some may move a mass only in a single direction.
Accordingly, an improved linear actuator may be useful.